Hi XYZ999RJ,
Thank you for contacting the Microsoft Community.
Allow me to provide information regarding the Cloud Ready Skill voucher code.
Please be aware that the error message usually occurs when the voucher code is already taken. Please be aware that all voucher codes are can only be used one time. With this, I would recommend you contact the voucher issuer to confirm why the voucher code it is not working.
You may submit a ticket below:
https://msftstudentcert.cloudreadyskills.com/support/newticket
If you have any other concerns, please don’t hesitate to let me know, I’d be happy to help!
Otherwise, if this solves your problem, please indicate “Yes” to the question and the thread will automatically be closed and locked. In case we do not receive a response, the thread will be closed and locked after one business day. Please be advised that after the case is locked, we will no longer be able to respond. If the resolution provided did not resolve the issue, please post a new question.
Regards,